熔焊是将焊接接头加热至(),不加压力而完成的焊接方法。
参考答案:熔化状态
Two middle-aged passengers fell into the sea. _______, neither of them could swim.
A.Actually
B.Unfortunately
C.Naturally
D.Luckily
随机接入的过程分为两类:()随机接入和()随机接入。